Learn about this topic in these articles:

history of Armenia

The first, unsuccessful, Arab raid into Armenia in 640 found the defense of the country in the hands of the Byzantine general Procopius and the
nakharar Theodor Rshtuni. Unable to prevent the pillage of Dvin in 642, Theodor in 643 gained a victory over another Arab army and was named commander in chief of the Armenian army by the Byzantine emperor Constans...